On Monday, 14 May 2012 at 16:41:39 UTC, Jonathan M Davis wrote:
On Monday, May 14, 2012 17:10:23 Roman D. Boiko wrote:
(Subj.) I'm in doubt which to choose for my case, but this is a
generic question.
http://forum.dlang.org/post/odcrgqxoldrktdtar...@forum.dlang.org
Cross-posting here. I would appreciate any feedback. (Whether
to
reply in this or that thread is up to you.) Thanks
For the question in general, there are primarily 2 questions to
consider:
1. Do you need inheritance/polymorphism?
don't have inheritance.
2. Do you need a value type or a reference type?
If you need inheritance/polymorphism, you have to use classes,
because structs
If you want a value type, you have to use structs, because
classes are
reference types.
If you want a reference type, then you can use either a class
or a struct, but
it's easier with classes, because classes are always reference
types, whereas
structs are naturally value types, so it can take more work to
make them
reference types depending on what its member variables are.
One other thing to consider is deterministic destruction. The
only way to get
deterministic destruction is to have a struct on the stack.
Value types will
naturally get that, but if you want a reference type with
determinstic
destruction, then you're probably going to have to use a
ref-counted struct.
In the vast majority of cases, that should be enough to decide
whether you
need a class or a struct. The main case that it doesn't is the
case where you
want a reference type and don't necessarily want a class, and
that decision
can get complicated.
In the case of a token in a lexer, I would definitely expect
that to be a value
type, which means using a struct.
- Jonathan M Davis
Semantics is clearly of value type. But it would be nice to
minimize size of instance to be copied. (I could simply split it
into two, if some part is not used in most scenarios.)
Just curious: how to implement a struct as ref type? I could add
indirection (but then why not just use a class?), or simply pass
by ref into all methods. Are there any other options?
Thanks to everybody for your feedback, it looks like I'll stay
with struct.
